In Rivalry Likened to Classical Drama, Roles Switch Again as Gillard Is Deposed in Party Ballot

SYDNEY—Kevin Rudd returned as Australia's prime minister after defeating Julia Gillard in a party leadership vote that marks a stunning turnaround for a figure she toppled three years ago but who has remained popular among voters.

Mr. Rudd's decisive 57-45 victory in the ballot among ruling Labor Party members on Wednesday seals his position as Australia's incoming prime minister—though to keep his leadership he will need to maintain...